Karl Bullock remembers:
I was a Radio Shack store manager back when the Model 16 (and later ther
6000) came out. We had sold a number of these machines to a local
business for use in their convenience stores. When Tandy released the
Model 16, they bundled a new version of TRSDOS with it - TRSDOS16 - and
advertised this as their next generation OS. Later versions of
TRSDOS16 were to include multiuser/multitasking capabilities, but the
initial version was single-user only. They also released some software
development tools.

When the programmer for our local business demanded to know when the
multi-user system would be out, I found that information was unavailable.
"Soon" was all the answer I could get. Finally, my customer
called John Roach, then President of Tandy, directly and demanded a copy of
whatever they had, or there'd be a lawsuit. I received a call from
Tandy HQ informing me that a pre-release version of the new OS would be
shipped to my store, and I was to follow certain procedures (have some
paperwork signed) before giving the OS to my customer.

When the package arrived, it was not TRSDOS16, but Xenix. The story
goes that the Tandy software people couldn't get the multi-user software
working, so they made a call to the then-unknown Bill Gates and bought his
port of Unix to the 68000. Inadvertently, I sold one of the first
versions of Xenix to my customer. Soon thereafter, the rest of the
world was informed of the change, and the rest, as they say, is history.
All this before IBM ever heard of Bill Gates. I always wondered what
kind of deal Bill made with Tandy.